The Lost Song
Trigger this one by speaking to the Biologist at the sentry post outside Techiix
He'll tell you of ancient whale-like creatures being hunted by poachers, and ask you to intercede. Do. Your navpoint will lead you to a poacher hideout.
Kill the hostiles, and read the datapad for your next location. This leads you a cave at the end of the 'moat' which encircles Kett Mountain. You'll encounter kett bases and Remnant sites on the way, but don't worry about getting distracted- this mission will keep.
Whne you are ready, storm the cave. There are many Iridium deposits squirreled away here, but your navpoint will draw you ineluctbly closer to a lone scientist.
Get closer and talk pragmatism- the scientist believes that the whalethings can be harvested to aid the war against the kett. You can choose to support this research or shut down the project- either way Jaal confesses he's nto certain which choice was right, and no one else ever mentions it.
You also get a Viability reward either way. Don't forget to scan the equipment here for data before departing.